In the present study, we focused on two inshore rockfish species. S. porcus and G. cobitis are predators mainly inhabiting rocky substrates of coastal waters (Harmelin-Vivien et al., 1989; Faria and Almada, 2006, 2009; Compaire et al., 2018).

Along with other scorpionfish species, the black scorpionfish is regarded as a key predator crucial to the proper functioning of rocky-reef ecosystems (D’Iglio et al., 2024). It is one of the main species, in terms of abundance and biomass, in the catches of several Mediterranean artisanal fisheries in Spain (Forcada et al., 2009), Italy (La Mesa et al., 2010), Turkije (Bilgin and Çelik, 2009) and Croatia (Stagličić et al., 2011), thus representing a large source of income as it is considered a valuable species for fish soup. It is mostly caught by means of passive set nets and the fishing effort towards this species has increased in some areas, with consequent reduction in stocks (Ferri et al., 2012; D’Iglio et al., 2024). S. porcus is a target species also for some recreational fishing activities e.g. spearfishing (Tiralongo, 2024) and LRF technique (Peksu et al., 2020).

The giant goby inhabits intertidal zones of rocky shores and acts as an indicator of the health of these ecosystems, which are facing several threats, as habitat degradation due to coastal development and pollution, and climate change (Claudet and Fraschetti, 2010; Sarà et al., 2014). G. cobitis is locally protected in the United Kingdom (Wildlife and Countryside Act 1981; Tillin and Riley, 2017), which represents the northernmost area of its distribution, expanding to the Atlantic coasts down to Morocco and including the Mediterranean. Although it is not targeted by commercial fisheries, the giant goby represents a gamefish for LRF anglers (Froese and Pauly, 2010).

The International Union for Conservation of Nature (IUCN) has listed S. porcus and G. cobitis as Least Concern in the Mediterranean Sea, although information on abundances and population trends of both species is currently scarce.

Two study areas were selected for the tagging programme ( Figure 1 ). Both are inshore locations within two Italian harbours of the north-western Adriatic Sea, i.e. Numana (Site 1; small touristic harbour) and Ancona (Site 2; large commercial harbour), consisting in semi-enclosed areas connected to the open sea through the main entrance of the harbours. The grounds of both sites are characterized by artificial blocks below the docks, surrounded by sandy bottom. Each site, measured in dock length, was divided into sub-areas (10 meters long) to take into account the exact place where the fish were caught, released and eventually recaptured. The main features of the study areas are listed in Table 1 .

A total of 88 fishing sessions were conducted from January 2024 to January 2025, covering all four seasons (31 in winter, 24 in spring, 21 in autumn, 12 in summer). Total fishing time amounted to 91.5 hours at Site 1 and 48 hours at Site 2, irrespective of the number of anglers. In each site and session, fishing operations were performed from the dock using the LRF technique by 1 to 5 experienced anglers, while one researcher witnessed as onsite observer. The fishing rods were 1.8-2.1 m long with casting weight of 0.5-15 gr, associated with 1000–2500 spinning reels spooled with 0.06-0.10 mm braided line and 0.20-0.28 mm fluorocarbon leader. The jig-heads used had hook size ranging from 2 to 8, and lead weight from 0.9 to 5 gr. The lures on the hook were largely the same across the entire study period: i) 4-7 cm long silicon shads and crabs as artificial bait; ii) pieces of deep-water rose shrimp (Parapenaeus longirostris) as natural bait. Additional baits (i.e. bread and anchovy, Engraulis encrasicolus) were used by interviewed anglers who recaptured tagged fish outside the monitored fishing operations. Each fishing session consisted in one or more anglers covering all the sub-areas and deploying the jig-head within the rocks below the docks. In sessions with multiple baits (artificial and natural), one angler used artificial bait and the other angler used natural bait. The jig-head was maintained in constant movement as typical in LRF and spinning techniques.

Targeted species caught (S. porcus and G. cobitis) were individually measured (total length, L, to the nearest 0.1 mm below), weighted (total body weight, W, to the nearest 0.1 g below), tagged by the researcher and released in the exact location where hooked. A T-bar anchor tag (Hallprint Fish Tags, Hindmarsh Valley, Australia) labelled with a unique five-digit identification number and a telephone number was placed below the dorsal fin of each fish. The air exposure time, which depended on unhooking, measuring and tagging procedures and/or photos before release was recorded. The fish handling process i.e. the retrieval, unhooking and tagging phases prior to release, was recorded as a two-category handling: i) good, if the fish did not fell to the ground or did not show any bleeding or evident damage; ii) poor, if the fish fell to the ground, showed bleeding or evident damage. Also, information on the fish vitality at release was recorded as a two-category instant vitality, based on visual inspection from both observer and fisher(s): i) good, i.e. the fish quickly swam away as soon as touching the water, with vigorous body movement; ii) poor, i.e. the fish rested for some second in the water with no reflexes and/or swam away in a slow manner with weak body movement or unbalanced. For all the other species caught in the sessions, only the individual weight was recorded.

For each fishing session, data on both air and water temperature was recorded. Information on recaptured fish (date, code, length, weight, location, bait type) was provided by researchers during fishing sessions (direct observation) or by fishers through the phone number printed on the tag (interview).

All analyses described below were performed within the R statistical environment (R Core Team, 2025).

Specific authorization was required for the fishing activities inside the two sampling sites, from both the Italian Coast Guard (Site 1) and private authority (Site 2). Protected species have not been involved in any part of the field studies. Ethical review and approval were not required because fish were sampled during recreational angling activities and were not subject to any experimental manipulation, in line with the Explanatory Note of the Italian Ministry of Health’s Directorate- General for Animal Health and Veterinary Medicinal Products (DGSAF) of July 26, 2017. Animal manipulation complied with the guidelines of the European Union Directive (2010/63/EU) and the Italian Legislative Decree 26 of March 4, 2014 “Attuazione della Direttiva 2010/63/UE sulla protezione degli animali utilizzati a fini scientifici”.

Overall, 17 species (16 fish species and 1 cephalopod species) were caught, respectively 15 in Site 1 and 9 in Site 2 ( Supplementary Table S1 ). Each LRF session monitored often resulted in more than 4 species caught. Most of the catches consisted of small fish belonging to the Gobiidae (4 species), Sparidae (3 species) and Blennidae (2 species) families. In Site 1, the catch was dominated by S. porcus, in both number of individuals and weight, followed by rock goby (Gobius paganellus); all the other species were caught in small amounts (less than 10 individuals). In Site 2, G. paganellus was the most abundant catch in both number of individuals and weight, followed, in number of individuals, by black goby (Gobius niger), G. cobitis and S. porcus. We decided not to tag individuals of G. paganellus or G. niger since: i) they are not considered target species of LRF technique; ii) the majority of them were too small to be tagged with T-bar anchor tag (dimensions: 2.5 cm in length, 0.1 g in weight). Further species were caught, in small amounts, only in Site 1 (n = 8) while fewer species were caught only in Site 2 (n = 2). Full species lists for both sites are provided in Supplementary Table S1 . Considering the total catch, the mean (± standard error) CPUE_w was 61.7 g ± 6.01 with artificial bait and 39.3 ± 5.97 with natural bait, with no significant differences detected (χ² = 1.34; p value = 0.25).

A total of 149 S. porcus (129 in Site 1; 20 in Site 2) and 38 G. cobitis (6 in Site 1; 32 in Site 2) were captured during the fishing sessions ( Supplementary Table S1 ). All the individuals were tagged, except for recaptured individuals (which were already tagged), resulting in 136 S. porcus and 38 G. cobitis. The length range was 9.0-27.4 cm for S. porcus and 10.2-26.9 cm for G. cobitis. The length-frequency distributions are represented in Figure 2 . Regarding S. porcus, in both sites, we observed the highest frequencies for individuals of 11-12 cm and 14-15 cm length ranges. By contrast, the largest individuals (above 19 cm) were caught only in Site 1. Regarding G. cobitis, all the individuals caught in Site 1 were above 15 cm, while in Site 2 we observed the highest frequencies for both smaller individuals (11-13 cm length range) and for individuals of 17-18 cm length range ( Figure 2 ).

We observed a significant difference between the CPUE of S. porcus and G. cobitis within the two Sites ( Figure 3 and Supplementary Table S2 ). The mean (± standard error) CPUE of S. porcus was significantly higher in Site 1 (CPUE_w 106.51 g ± 18.16 and CPUE_n 1.11 ± 0.17) than in Site 2 (CPUE_w 31.12 g ± 8.54 and CPUE_n 0.51 ± 0.14). By contrast, a significantly higher CPUE for G. cobitis was observed in Site 2 (CPUE_w 39.91 g ± 10.00 and CPUE_n 0.69 ± 0.12), when compared to Site 1 (CPUE_w 7.50 g ± 4.23 and CPUE_n 0.07 ± 0.04; Figure 3 and Supplementary Table S2 ).

Length-weight relationships of both S. porcus and G. cobitis are presented in Supplementary Figure S1 . Both species displayed isometric growth (S. porcus: b = 3.04, a = 0.02; G. cobitis: b = 3.01, a = 0.01), indicating that individuals generally maintain their shape and proportions as they increase in size. In both species, the model well fitted the data (S. porcus: R² = 0.98; G. cobitis: R² = 0.97).

Each angling event i.e. from hookset to fish landing, lasted from 0 to 5 seconds, mainly depending on the fish size. Since the anglers immediately hooked the fish after feeling the bite on the jig-head, very few individuals ingested the hook (3 individuals of S. porcus and 1 individual of G. cobitis).

The air exposure time ranged from 1 to 15 minutes (mean 3.1 ± 0.11) and varied according to different unhooking and handling times. The handling of the fish was good in 71.8% of the cases for S. porcus and 76.3% of the cases for G. cobitis ( Supplementary Table S3 ). The instant vitality of released fish was higher in S. porcus (96.0%) than in G. cobitis (76.3%; Supplementary Table S3 ). The tagging process did not produce any mortality event before release and did not apparently affect the vitality of tagged fish.

No concerning multicollinearity was detected, as the highest pairwise Pearson correlation coefficient among predictors was 0.25 (between fish length and air exposure). The final model, selected by bidirectional stepwise AIC, retained air exposure time, species and their interaction as predictors ( Supplementary Table S4 ). This model, having the lowest AIC (93.37; Supplementary Table S4 ), showed that individuals of S. porcus had a significantly higher probability of good vitality once released compared to G. cobitis (p value < 0.001), indicating a species-specific difference in resilience to capture. Although the air exposure time did not reach statistical significance (p value = 0.25 regardless of the species), it showed a negative association with vitality in S. porcus (p value = 0.07), indicating a decline in vitality with increased air exposure time ( Table 2 ).

Table 3 reports the number of recapture events out of the total tagged fish, while Table 4 lists each recapture event recorded for both species, with information on dates, handling, vitality and eventual lure (or gear) switching, sub-area change, length range and increment in total length. The tag-recapture data was obtained both during the fishing sessions (observer modality) and through fishers’ interview until 30^th April 2025. Figure 4 illustrates the capture and recapture timelines for all individuals recaptured during the study.

A total of 34 recapture events were recorded ( Table 4 ). Regarding S. porcus, 32 recapture events were recorded (31 in Site 1 and 1 in Site 2). During the fishing sessions, 13 recapture events were observed. Further 19 recapture events were recorded thanks to fishers that contacted the authors through the phone number printed on the tag: 17 of them were caught using rod and reel, mainly through LRF technique, while 1 was caught in a fyke net commonly employed in artisanal fishery of the area (Petetta et al., 2020). Two S. porcus specimens were recaptured multiple times: one was caught five times and another was caught two times ( Table 4 ). Without considering the multiple recapture events for the same individuals, the tag-recapture rate was 19.9% (27 distinct individuals out of 136 tagged) regardless of the site; however, we observed a marked difference between Site 1, with a tag-recapture rate of 22.4% (26 out of 116 tagged), and Site 2, where 1 fish was recaptured out of 20 tagged (5.0%; Table 3 ). Recapture events of S. porcus were recorded throughout the study period, with highest frequencies in autumn 2024, spring 2024 and winter 2025, respectively ( Table 4 ; Figure 4 ).

Regarding G. cobitis, only 2 individuals were recaptured (1 in Site 1 and 1 in Site 2), both thanks to anglers that were interviewed. The resulting tag-recapture rate was 5.3% (2 out of 38 tagged) but again with a marked difference between Site 1 (16.7%; 1 out of 6 tagged) and Site 2 (3.1%; 1 out of 32 tagged; Table 3 ).

We failed to identify 2 recaptured individuals (1 S. porcus and 1 G. cobitis), since the interviewed anglers did not record the unique code printed on the T-bar tag ( Table 4 ). Regardless of the species, the days at liberty ranged from 0 to 197 days (mean 55.6 ± 9.4 err. std.).

We addressed the effort and impact of recreational fishing in coastal marine habitats, through the LRF technique. LRF can be included in what is called “micro fishing”, a term increasingly used to describe recreational angling that targets small-bodied fish, including species that remain small as adults or the early-life stages of larger species. This concept was originally popularized within angler communities and has recently been introduced into the scientific literature to describe emerging recreational fishing behaviours, particularly those that differ from traditional trophy-oriented angling (Cooke et al., 2020). One goal of this activity is to encounter as many species as possible, often with C&R practices, and sometimes creating a so-called “life-list” of the species caught (Cooke et al., 2020). LRF is becoming more and more widespread among Mediterranean and Black Sea anglers due to the practicality of the gear, which only requires silicon lures and light sinkers (Peksu et al., 2020).

In the present study, we often observed many species caught in each monitored LRF session, with a total of 17 different species. The difference observed in species composition between the two coastal sites, despite being spatially close (around 20 km distance between them) might be related to a slightly different habitat. Both are similar semi-enclosed areas within harbours, and the main difference is related to depth, with Site 1 having deeper habitats (1 to 5 m) than Site 2 (0 to 2 m), which might attract more species (15 vs 9 species; Table 1 ). Greater depth, even on a small scale, can provide a wider range of microhabitats and environmental gradients (e.g. light, temperature, shelter), potentially supporting higher species richness (Gratwicke and Speight, 2005; Ellis et al., 2012). The higher anthropogenic impact of Site 2, inserted in a large commercial harbour, could also prevent the presence of some species that were instead caught in Site 1, which belongs to a significantly smaller touristic harbour. We also observed significant differences in the catches of the two target species (black scorpionfish and giant goby), highlighting a clear habitat separation between them. The shallower grounds of Site 2 seemed to be suitable only for immature individuals of S. porcus, while Site 1 was frequented by all the sizes of the species. The preference of younger and smaller individuals for shallower habitats is consistent with ontogenetic niche shifts aimed at reducing predation or competition pressure (Werner and Gilliam, 1984). By contrast, the significantly higher amounts of G. cobitis caught in Site 2 compared to Site 1 confirm the tendency of the species of inhabiting the upper sheltered shores of the intertidal zone (Wheeler, 1993; Compaire et al., 2022), while only few large individuals were caught in the deeper grounds of Site 1.

Here, we applied conventional tags and gathered data from recapture events to gain insights on the fate of released fish and to derive some useful biological data in terms of growth and spatial movements. Overall, the frequent recapture events observed for S. porcus highlights the vulnerability of this species to recreational fisheries, especially in semi-enclosed areas such as harbours or docks. The high recapture rate observed for this species is in accordance with what found in literature, where scorpionfish usually have the highest recapture rates, when compared to other species (Hanan and Curry, 2012). We also observed an intra-specific variability, since two S. porcus specimens were recaptured multiple times, many others one time, while the majority was never recaptured. Interestingly, there was a marked difference between the two sites, with Site 1 including almost all the recapture events for both species. This may be due to the wider area of Site 2, which could have hampered detailed research of the fish within the rocks as it happened in Site 1. Recapture events were more frequent in seasons where a higher fishing effort was exerted.

C&R in angling can be compared to discarding in commercial fisheries, even if fish caught and released by anglers usually experience better conditions and less damage than those caught by most commercial fishing gears (Cooke and Wilde, 2007). Nevertheless, no form of angling is entirely risk-free for fish, and understanding survival/mortality rates of released individuals remains central to C&R scientific studies.

In the present work, we estimated the effects and consequences of C&R on S. porcus and G. cobitis, two species characterized by slow growth rates and relatively short lifespans (maximum lifespan of around 10 years for both species; La Mesa et al., 2010; Tillin and Riley, 2017). Both species can be caught as target or bycatch through all inshore angling techniques employing sinker and bait in rocky shallow waters or through spearfishing (Tiralongo, 2024). S. porcus is also a shared resource between Mediterranean recreational and artisanal fisheries, being an important catch and source of income in the coastal passive set nets and traps (Ferri et al., 2012; Özgül et al., 2019). For this species, a general decline in catches and average size has been observed in different areas due to fishing activities (D’Iglio et al., 2024; Tiralongo, 2024), and thus a closure of fisheries during the spawning season and the establishment of a minimum landing size have been suggested (Bilgin and Çelik, 2009). Therefore, assessing the impact of C&R practices in angling towards these species contribute to understand the potential threats of the fisheries sector to marine resources.

We correlated the instant vitality of released fish with some of the factors that are known to most affect survivability and post-release effects (Bartholomew and Bohnsack, 2005). These were water temperature, which is the most important environmental parameter; fish length, which reflects different life stages (e.g. immature and mature) and angler behaviour, categorized into air exposure time and handling of the fish. We did not consider the barotrauma effects, due to the shallow depths (less than 5 meters), the hooking location, since the fish is usually not given time to ingest the hook with LRF technique, or the eventual predation after release, since the study areas rarely host larger predators in shallow rocky bottoms, and no predation events were observed. Although the air exposure time did not significantly affect post-release vitality in our model, it showed a negative trend for S. porcus, consistent with the hypothesis that prolonged air exposure may reduce the chances of recovery after release. It is in fact known that fish exposed to air suffer from cardiac disturbances and physiological homeostasis disruptions (Bartholomew and Bohnsack, 2005; Cooke et al., 2013) which can cause lethal and sub-lethal effects, especially with longer durations (Cooke and Suski, 2005; Cook et al., 2015). Air exposure was shown to affect mortality, recovery times, stress, swimming performances, reproductive fitness of several saltwater and freshwater fish species (Schisler and Bergersen, 1996; Richard et al., 2013; Blyth and Bower, 2022; Butler et al., 2022). While the association with vitality was not statistically conclusive in our dataset, its direction and ecological plausibility support further investigation, especially in studies with larger sample sizes or higher variation in exposure times.

Usually, a good instant vitality is not directly linked to survivability in the longer term (Petetta et al., 2025); however, the frequent recapture events observed for scorpionfish, with all recaptured individuals showing a good vitality at first release, are a definitive proof of their survivability. The less percentage of G. cobitis specimens showing good vitality after release (76.3% vs 96% of S. porcus), which was not significantly related with increasing air exposure time, poor handling, water temperature or fish length, may derive from a stress of the capture event itself. This is observed also in the lower recapture rates compared to scorpionfish, which may indicate a higher mortality or other C&R effects (modified behaviour after release, better memory of the capture event etc.). More detailed information and observations, especially on the sub lethal physiological and behavioural consequences of C&R, can be obtained by further studies using biotelemetry technology (Donaldson et al., 2008). For smaller specimens, which are frequently caught in coastal habitats (e.g. the individuals of G. paganellus of the present study), alternative tagging techniques such as visible implant elastomer tagging could be considered (Roma et al., 2018; Compaire et al., 2022).

The isometric growth, estimated for S. porcus by length-weight relationship, is in accordance with what observed by La Mesa et al. (2010) in the same area and differs from results obtained in Aegean Sea (negative allometric growth; Moutopoulos and Stergiou, 2002; Karakulak et al., 2006) and Black Sea (positive allometric growth; Bilgin and Çelik, 2009; Demirhan and Can, 2009). Some authors suggested the presence of a distinct population of S. porcus in the Adriatic Sea (Ferri et al., 2010; D’Iglio et al., 2024), with a weak east/west genetic differentiation observed within this basin (Boissin et al., 2016).

The estimated values of asymptotic size and body growth rate for S. porcus, although with relatively wide confidence limits (L_∞= 26 cm ± 5.25 and k = 0.21 ± 0.09), were similar to those calculated in the same area by La Mesa et al. (2010) from natural reefs (L_∞ = 22.3 cm and k = 0.23). Similarly, the mean annual growth rate calculated for our specimens was between 2.0-2.1 cm/year (corresponding approximately to a modal size of 14-16 cm), closely resembled that reported from natural reef for fish between 14.1 and 16.6 cm (La Mesa et al., 2010, Table 3 ). The observed decrease in daily growth rate with increasing body size aligns with the well-documented pattern of growth deceleration as individuals approach their asymptotic size (Pauly, 1981). It is worth to note the high variability in individual growth rates observed in the field due to relatively large size range of fish sampled and, possibly, to the different seasons of the catch/recapture events.

The information of conventional tagging employed in this study is limited to the date and position at release and at recapture; however, we could derive some patterns in the site fidelity of the recaptured fish. The high tag-recapture rate observed for S. porcus in the same site, and often in the same sub-area, highlights its sedentary lifestyle or at least its high site fidelity. These results are in line with what observed for the same species by Özgül et al. (2019) by using acoustic telemetry on adult individuals in artificial reefs. We instead observed that the majority of recaptured S. porcus were juveniles, suggesting that shallow rocky areas within harbours may have a key role as nursery area for this species, as observed in rocky intertidal pools (Compaire et al., 2022). By contrast, mature individuals (i.e. above the length at first maturity of 17 cm; La Mesa et al., 2010) could use them only as temporary sites for feeding or for reproduction purposes. In fact, the few recapture events of these larger individuals in the same site after more than 10 days may be a sign that they leave the site, and the individual recaptured at 24 km distance from the first catch may support this hypothesis. As observed by La Mesa et al. (2010) in the same study area, adult populations of S. porcus may find the ideal habitat in offshore artificial reefs with deeper waters (10-40 m), which are not frequented by juveniles. From a management perspective, the observed site fidelity of S. porcus, particularly in juveniles, suggests that area-based conservation measures, such as spatial closures or the designation of nursery habitats within harbours, could be effective in protecting early life stages (Cooke and Cowx, 2006). These localized management strategies could help reducing the catch of immature and undersized individuals of several species which are known to inhabit shallow waters and to be frequently caught by shore recreational fisheries (Erbay et al., 2024; Iborra et al., 2024).

Very few studies estimated growth rates for G. cobitis (Koutrakis and Tsikliras, 2003; Compaire et al., 2020); the observed isometric growth is in accordance to what found in Aegean Sea (Koutrakis and Tsikliras, 2003). This species is known to be a sedentary species, often inhabiting intertidal rock pools with high site fidelity (Compaire et al., 2022) but with microhabitat shifts following tide changes (i.e. moving to deeper channels during low-tides; Faria and Almada, 2009). No sufficient data was available on G. cobitis to determine a growth rate trend. The only individual of G. cobitis for which we had length information was within the 21-23 cm length range, i.e. above the length at first maturity observed for the species (12-13 cm; Tillin and Riley, 2017). Our relatively low tag-recapture rate for this species contrasts with what found by Compaire et al. (2022) (mean recapture rate of 38.9% by using anaesthetic and hand nets on rock pools) and therefore might be related to the angling process that may have influenced survivability and behaviour, as stated above. In fact, G. cobitis is considered highly resilient and able to migrate in and out of an area impacted by pollution or habitat alteration (Tillin and Riley, 2017), and thus it may escape from an area or hide to avoid angling. External tags may have further affected G. cobitis, which relies on moving through narrow crevices, potentially altering its natural behaviour more than in S. porcus, which tend to remain more exposed on the substrate.